Your models seem to be quite good and you seem to be a competent model-builder. You will need more models with a signature style to begin attracting attention. More importantly, you will need to take a broad look at what people are doing with various kinds of 3D models - in games, in advertising, in landscape architecture, and on hobby sites where people buy models to make amatuer scenes for their own enjoyment.
For example, one thing that I think is happening over the long term is that hobbyists who once used sites like Daz, Renderosity and Cornucopia are growing older and beginning to pass away. So the market for inexpensive "props" for amateurs making scenes and renders for their own enjoyment is starting to go away. The younger people who might have replaced them are instead playing computer games, and their derived form of hobbies focus on printable collectables of anime figures and the like. So, as an example of a "trend", the "inexpensive" 3D marketplace is shfting from utilitarian "props" of every kind to sculpted, printable figurines of every kind. Right now, if you had sculpting skills, you could probably sell almost any figurine based on the latest Avatar movie.
Anyhow, you need to sit back and take a very long look at what things people who traffic in 3D models seem to be doing with their leisure and with their professional time. It would be important to consider whether you want to go after the professional markets of some kind (interior decoration, landscape architecture, jewelry creation, etc.) or the ameteaur markets (gamers, collectors of figurines, spaceship enthusiasts, cosplay people who need costume components, people who want a one-off piece of jewelry for a loved one, etc.)
Also, you need to be a good student of the technology and its changes. For example, for the last ten years, semi-photorealistic character models were at a premium, and sold well because they were relatively hard to make. But over the last year and a half, technology has changed so that animateablecharacters can be made by almost anyone. When these kinds of technological changes occur, the model-builders that survive are those who make unique, rather than utilitarian creations. Those who can develop a distinctive and attractive style. So, for any well established market for props, if you want to work in that area, you need to focus on developing a unique style. (For example, if you want to make models of guns, you'll need to find a niche of some kind (old Soviet guns, WWII German guns, old USA Wild West rifles) because there are thousands of 3D gun models in the 3d world - most overpriced by now. Alternatively, you can chose to work in a developing area of technology where the work is hard, the tools are incompletely developed, and the products seem over-priced as a result. Truely high-definition characters (rigged and with facial animation possibilities), high-end jewelry design - partner with a professional jewelry designer, become a specialist in mass character creation and movement for archtects needing to render buildings with crowd scenes, and those sorts of things. Basically, you move into a field that is currently "difficult" and then start producing a good suite of products at a price somewhat below what it costs you to build just one of those kind of things in that field. Your profit comes from becoming very efficient (lowering your own cost) at building some kind of thing that is cost ineffective if you only built one product - within a field that is new - developing - somewhat difficult - and typically where the 3d modelling tools are not quite what they need to be.
